C语言常用函数

函数名: abort

功能: 异常终止一个进程

用法: void abort(void);

程序例:

#include

#include

int main(void)

{

printf("Calling abort()\n");

abort();

return 0; /* This is never reached */

}

函数名: abs

功能: 求整数的绝对值

用法: int abs(int i);

程序例:

#include

#include

int main(void)

{

int number = -1234;

printf("number: %d absolute value: %d\n", number, abs(number));

return 0;

}

函数名: absread, abswirte

功能: 绝对磁盘扇区读、写数据

用法: int absread(int drive, int nsects, int sectno, void *buffer);

int abswrite(int drive, int nsects, in tsectno, void *buffer);

程序例:

/* absread example */

#include

#include

#include

#include

int main(void)

{

int i, strt, ch_out, sector;

char buf[512];

printf("Insert a diskette into drive A and press any key\n");

getch();

sector = 0;

if (absread(0, 1, sector, &buf) != 0)

{

perror("Disk problem");

exit(1);

}

printf("Read OK\n");

strt = 3;

for (i=0; i<80; i++)

{

ch_out = buf[strt+i];

putchar(ch_out);

}

printf("\n");

return(0);

}

函数名: access

功能: 确定文件的访问权限

用法: int access(const char *filename, int amode); 程序例:

#include

#include

int file_exists(char *filename);

int main(void)

{

printf("Does NOTEXIST.FIL exist: %s\n",

file_exists("NOTEXISTS.FIL") "YES" : "NO"); return 0;

}

int file_exists(char *filename)

{

return (access(filename, 0) == 0);

}

函数名: acos

功能: 反余弦函数

用法: double acos(double x);

程序例:

#include

#include

int main(void)

{

double result;

double x = 0.5;

result = acos(x);

printf("The arc cosine of %lf is %lf\n", x, result); return 0;

}

函数名: allocmem

功能: 分配DOS存储段

用法: int allocmem(unsigned size, unsigned *seg); 程序例:

#include

#include

#include

int main(void)

{

unsigned int size, segp;

int stat;

size = 64; /* (64 x 16) = 1024 bytes */

stat = allocmem(size, &segp);

if (stat == -1)

printf("Allocated memory at segment: %x\n", segp);

else

printf("Failed: maximum number of paragraphs available is %u\n", stat);

return 0;

}

函数名: arc

功能: 画一弧线

用法: void far arc(int x, int y, int stangle, int endangle, int radius);

程序例:

#include

#include

#include

#include

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy;

int stangle = 45, endangle = 135;

int radius = 100;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult(); /* an error occurred */

if (errorcode != grOk)

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

setcolor(getmaxcolor());

/* draw arc */

arc(midx, midy, stangle, endangle, radius);